180 



PRACTICAL DRAINAGE 



"If only the required capacity of the drain were con- 

 sidered, it would be found feasible to do a great deal of 

 drainage with 4-inch and 5-inch tile, but experience has 

 shown that the use of tile smaller than 5-inch is not satis- 

 factory, while 5-inch should be used only for short branch 

 lines or at the upper ends of branch lines. The following 



(a) (b) 



FIG. 26. TYPES OF LUMBER DRAINS USED TO 

 RECLAIM BOGGY ALKALI LAND. 



table is offered for purposes of comparing the carrying 

 capacity of tile lines of different sizes, on the assumption 

 that all are laid on the same grade. 



TABLE XIX. RELATIVE CARRYING CAPACITIES OF TILE OF 

 DIFFERENT SIZES 



One 



6-inch tile 



7-inch tile 



8-inch tile 



lo-inch tile 



i2Mnch tile 



Will carry the discharge of 



Two 5-inch tiles 



One 6-inch and one 5-inch tile 



Two 6-inch tiles 



One 8-inch tile and one 7-inch tile 



One lo-inch, one 8-inch, and 5-inch tile; or three 



8-inch tiles; or seven 6-inch tiles; or twelve 



5-inch tiles 



